Allis-Chalmers G Project Questions
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Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=48190
Printed Date: 27 Aug 2025 at 11:08am
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Topic: Allis-Chalmers G Project Questions
Posted By: KD8NGV
Subject: Allis-Chalmers G Project Questions
Date Posted: 30 Mar 2012 at 3:20pm
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I am working on my newly acquired G. The one thing I noticed is there is a pipe facing downwards coming out of the Valve cover. What is this and what does it mean if there is something coming out of it while running? Thanks, Kevin
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Replies:
Posted By: Roddo
Date Posted: 30 Mar 2012 at 3:30pm
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Its just a crankcase vent. Usually if you have oil slobbering out of it that means you have a bit of blowby in your engine. |
Posted By: KD8NGV
Date Posted: 30 Mar 2012 at 5:03pm
| It is pushing out a vapor of sorts... What would that mean? |
Posted By: Burgie
Date Posted: 30 Mar 2012 at 6:18pm
 ------------- "Burgie" |
Posted By: Burgie
Date Posted: 30 Mar 2012 at 6:20pm
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Kevin, There is a picture of that half scale G. ------------- "Burgie" |
Posted By: JoeM(GA)
Date Posted: 30 Mar 2012 at 7:41pm
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kevin, check your messages
------------- Allis Express North Georgia 41 WC,48 UC Cane,7-G's, Ford 345C TLB |
Posted By: KD8NGV
Date Posted: 01 Apr 2012 at 5:56pm
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That's a nice lloking half scale!!
What would that vent pushing out a vapor of sorts mean?
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Posted By: Burgie
Date Posted: 02 Apr 2012 at 6:02am
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Could be worn rings or cylinder bores. ------------- "Burgie" |
Posted By: KD8NGV
Date Posted: 02 Apr 2012 at 10:48am
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Please excuse the green behind my ear.... How might I go about checking that? I assume I need to take the head off the tractor, but how do I check the rings and bores? Do I look for slop? Or what?
Thanks guys?
Kevin
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Posted By: Gary in da UP
Date Posted: 02 Apr 2012 at 10:59am
| Inspect the plugs, do a compression test. Start there and post the results. In the meantime get manuals for your tractor.. You need them. |
Posted By: KD8NGV
Date Posted: 02 Apr 2012 at 11:01am
| I have all of the manuals for the tractor, I'll refer to them as I tear her apart. Ill take a look at the plugs tonight. Compression tested by thumb test or do I need a set of gauges? |
Posted By: JohnCO
Date Posted: 02 Apr 2012 at 11:12am
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KD, You can get a compression gauge at most any store selling auto parts, shouldn't cost much more then ten bucks for a simple one. You really need an accurate number on each cylinder, should be around 120 PSI as I remember. If one cylinder is quite a bit lower then the others, that might suggest a leaky valve but if there is blowby coming out of the breather tube, it is probably worn piston rings. If it runs ok and you aren't doing a lot of work with the tractor, you may just put off spending much money on it until it gets worse. Someone here will have better advice.
------------- "If at first you don't succeed, get a bigger hammer" Allis Express participant |
Posted By: mmccarty
Date Posted: 03 Apr 2012 at 5:31pm
As other have said, it's a crankcase vent. All engines have a certain amount of leakage past the compression rings (blowby). Without a vent it would pressurize the crankcase and cause problems with the oil seals. On a modern engine this vent would be plumbed backed into the engine intake and the gases would be reburned as an emissions control measure. They refer to this as Positive Crankcase Ventilation (PCV). It's normal to see a small amount of vapor leaving the vent. If it's blowing oil out on the ground, then the blowby is rather excessive and indicative of worn rings.
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KD8NGV wrote: